The project is intended to monitor changes in dental plaque organisms, specifically Strep. mutans, during fluoride preventive procedures provided to a school population. Serotypes of Strep. mutans are characterized and enumerated in plaque from individuals using fluoride rinses either daily or weekly, as well as from individuals using a placebo solution. Fluorescent Antibody (FA) reagents specific for the serotypes of Strep. mutans are employed to detect changes in plaque samples obtained from school students. The study is intended to determine major plaque changes during the course of fluoride therapy and to relate these changes to the caries reductions in each group.